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From: david@eng.sun.com (Big Ed's Gas Farm)
Newsgroups: comp.arch
Subject: Re: fork() vs vfork() and COW
Message-ID: <476@exodus.Eng.Sun.COM>
Date: 10 Jul 90 06:00:05 GMT
References: <1122@sirius.ucs.adelaide.edu.au> <3830012@hpcupt1.HP.COM> <58053@bbn.BBN.COM>
Sender: news@exodus.Eng.Sun.COM
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>While I can't claim the fork-exec with COW
>is faster than vfork-exec, I claim that it is not significantly slower in
>most cases...

I timed a simple test program on a Sun 4/60 running SunOS 4.1 (has COW):

#include <signal.h>
#include <vfork.h>

main(argc)
	int argc;
{
	int i, pid;

	signal(SIGCHLD, SIG_IGN);

	for (i = 0; i < 10000; i++) {
		pid = argc > 1 ? vfork() : fork();
		if (pid == 0)
			exit(0);
	}
}

% time ./a.out (fork)
0.2u 4.3s 0:09 47% 0+140k 0+0io 0pf+0w
% time ./a.out x  (vfork)
0.0u 4.1s 0:04 92% 0+140k 0+0io 0pf+0w

fork() seems to take twice as long as vfork() for a small process.

Of course if exec() is sufficiently slow you're right, this will not be
significant.

--
David DiGiacomo, Sun Microsystems, Mt. View, CA  david@eng.sun.com